JPH0132271B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a gasket made by kneading and vulcanizing a fiber material and a rubber material. Conventionally, heat resistance and durability are required for sealing members that prevent engine cooling water from leaking, such as at the joints of automobile engine water pumps, so gaskets made by kneading and vulcanizing asbestos fibers and rubber materials have been used. (generally called asbestos joint sheet) is widely used. However, in recent years, as engines have become lighter, the wall thickness of water pump flanges has been thinned, the diameter of flange tightening bolts has been reduced, and the number of bolts has been reduced. If the structure is such that it cannot be applied sufficiently, the tightening surface pressure is low, so the gasket does not fully fit into the flange, causing problems such as water leaking from the contact surface with the flange. . On the other hand, paper gaskets used as other sealing members are softer than asbestos joint sheets, and have good initial sealing performance even with low tightening surface pressure, but this is due to the presence of oil impregnated inside. The problem is that the sealant gradually dissolves into water, reducing sealing performance. This invention was made in order to solve the above problems, and in particular, the characteristics of the gasket made of the above-mentioned fiber material and rubber material are utilized as they are, and even at low tightening surface pressure, water on the contact surface is prevented. The main purpose of this invention is to provide a gasket that exhibits excellent water-sealing properties and a leak-proof function. The gasket according to the present invention has a core material composed of a gasket material mainly made of fiber material and a rubber material mixed with a mainly fibrous water-insoluble water-swellable substance, and the gasket material mainly contains powder. It is characterized by a structure in which the surface material composition is a mixture of a water-insoluble water-swellable substance, and the core material and the surface material laminated on both sides are vulcanized and molded into a three-layer sheet shape. When the water-swellable substance contacts water and swells, the gap between the gasket and the flange and the gap in the gasket material are filled, thereby preventing contact surface leakage and substance leakage. This is how it was done. The appropriate blending ratio of the fibrous material and the rubber material, which are the main materials of the gasket, is in the range of 50 to 90% by weight of the fibrous material and 10 to 50% by weight of the rubber material. In that case, the amount of fibrous material in the gasket material
If the amount of fiber material is less than 50% by weight (the amount of rubber material is 50% by weight or more), the tensile strength and heat resistance of the gasket tend to decrease; below), the sealing performance of the gasket tends to deteriorate.
The blending ratio of the fiber material and the rubber material is preferably selected within the above range. The fiber materials constituting the gasket material include inorganic fibers and/or phenol fibers such as asbestos fibers, glass fibers, carbon fibers, and metal fibers;
Organic fibers such as cellulose fibers can be used alone or in combination. Further, as the rubber material, SBR, NBR, natural rubber, etc. can be used alone or in combination. Examples of water-insoluble water-swellable substances to be added to the core material composition and surface material composition include carboxyl groups, sulfonic acid groups, phosphoric acid groups, quaternary ammonium bases, amino groups, imino groups, and viridinium bases. Natural or synthetic new water-based and water-insoluble polymer substances containing ionizable groups such as or salts thereof and/or nonionic hydrophilic groups such as hydroxyl groups, ether groups, amide groups (chain or cyclic), and nitrile groups. For example, a copolymer of acrylic acid or a salt thereof and divinylbenzene, a copolymer of acrylonitrile and vinyl chloride or vinylidene chloride, and one or more ethylene monomers copolymerizable with them. a formaldehyde crosslinked product of a polymer obtained by hydrolyzing an acrylonitrile polymer with an alkali, a formaldehyde crosslinked product of an acrylamide copolymer, a formaldehyde crosslinked product of an acrylamide copolymer, a combination of 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate, Acrylic polymers such as copolymers, copolymers of N,N-dimethylaminoethyl methacrylate and N,N'-methylenebisacrylamide; acid condensates of polyacrylic acid and polyvinyl alcohol, and Ebichlor of polyvinyl alcohol Polyvinyl alcohol polymers such as hydrin crosslinked products, phosphoric acid condensates of polyvinyl alcohol, and dried saponified copolymers of vinyl esters and ethylenically unsaturated carboxylic acids or their derivatives; starch heating condensates under acidic conditions , starch-based polymers such as saponified products of starch-acrylonitrile graft copolymers; 2-methyl-5
-Nitrogen-containing cyclic polymers such as copolymers of vinylpyridine and N,N'-methylenebisacrylamide, copolymers of N-vinyl-2-pyrrolidone and ethylene glycol dimethacrylate; radiation irradiation of polyoxyethylene These are crosslinked polyoxyethylene polymers. Further, the water-insoluble water-swellable substances include powdery substances and fibrous substances, each of which has the following characteristics. That is, the powdery water-swellable substance has the advantage that it has greater water absorption than the fibrous substance, and is easy to mix uniformly into the gasket material.Furthermore, when it swells, particles flow from the inside of the gasket to the surface. The particles that move and swell tend to concentrate on the gasket surface, and these swollen particles have the advantage of being highly effective in preventing contact surface leakage. It tends to break away from the surface and spill out into the fluid, so it lacks long-term durability. On the other hand, the fibrous water-swellable substance becomes entangled with the fibrous material in the gasket material during the kneading process with the gasket material, and due to this entanglement, it is retained in the gasket even when it swells.
It does not leak out into the liquid and therefore has excellent durability, but due to the entanglement of its fibers,
Because there is no migration to the surface when swelling, unlike in the case of powder, the amount of swelling material present on the surface is smaller than in the case of powder, and it is also easier to mix with the gasket material evenly than with powder. Due to uneven dispersion, unevenness is created on the gasket surface.
The sealability is sometimes inferior to that of powder. This invention utilizes the respective advantages of the above-mentioned powder-like swellable material and fibrous water-swellable material.
As mentioned above, as a water-insoluble water-swellable substance,
The core material is mainly fibrous, and the surface material is mainly powder, and as shown in Figure 1, it has a three-layer structure of core material 1 and surface materials 2 and 2. It is. The gasket with the above-mentioned three-layer structure is prepared by kneading the core material composition and the surface composition. First, the surface material kneaded material is placed on a calender roll to form a surface material layer, and then the core material kneaded material is added to the surface material layer. It can be easily obtained by adding the surface material kneaded material, forming a core material layer on the surface material layer, and finally adding the surface material kneaded material and forming it on the core material layer, followed by vulcanization molding. . In preparing the core material composition, it is appropriate that the proportion of the water-insoluble fibrous water-swellable substance blended into the gasket material ranges from 1 to 23% by weight based on the total amount. If the water-swellable substance is added in a large amount, the tensile strength of the gasket will be reduced, so it is preferable to use the minimum necessary amount. Further, the preferable fiber length range of the fibrous water-swellable substance is 0.1 to 10 mm, more preferably 0.2 to 10 mm.
It is 5mm. If the fiber length is 0.1 mm or less, there is a strong tendency for it to bulge out into the water, similar to granular fibers, and if the fiber length is 10 mm or more, it becomes difficult to mix uniformly into the gasket material. On the other hand, in preparing the surface material composition, it is appropriate that the blending ratio of the water-insoluble powder water-swellable substance to be blended into the gasket material is in the range of 1 to 38% by weight based on the total amount. The shape of the powder may be granular, scaly, acicular, etc., and its size is as follows:
In the case of scales, the average scale diameter is preferably 1 mm or less, and in the case of needles, the needle length is preferably 1 mm or less, preferably 100 μm or less. Regarding the degree of water swelling (ratio of the amount of water that can be absorbed to its own weight) of the water-swellable substance, the larger the degree is, the smaller the amount of the water-swellable substance to be blended is preferable. Fibrous water-swellable substances with a water swelling degree of 30 to 500 times are used. In a gasket having a three-layer structure in which surface materials are laminated on both sides of the core material layer, the thickness of the surface material is 1/3 or less of the total thickness of the gasket, and is preferably 10 μ or more. If the thickness exceeds the above range, problems such as drop-off of particles during swelling and a decrease in tensile strength will occur, and if the thickness is below the above range, there is a risk that the sealing performance will deteriorate. According to the gasket constructed as described above, since a fibrous water-swellable substance is used as the core material serving as the base of the gasket, the detachment phenomenon of the water-swellable substance does not occur during swelling. On the other hand, since a powdery water-swellable material is used for the surface material, it is possible to form a smooth surface, and a large number of swelling particles gather on the surface of the gasket, and the rate of water absorption and swelling improves, making contact easier. Surface leakage is reliably prevented and extremely excellent sealing performance is achieved. In that case, the powdery water-swellable substance contained in the surface material tends to separate from the gasket body when it swells, but since the thickness of the surface material layer is thin compared to the overall thickness of the gasket, the surface material shown above Within the range of the thickness of the material layer, the effect is small and can be ignored. Therefore, according to the present invention, it is possible to obtain a gasket that has both excellent water sealing properties and long-term durability. Next, in order to facilitate understanding of this invention, Examples are shown below, but the gist of this invention is not limited by the description of these Examples. Example A gasket material consisting of asbestos, rubber, a vulcanizing agent, and a filler is blended with a water-insoluble fibrous water-swellable substance in the proportions shown in Table (1) as a core material composition. A surface material composition is prepared by blending a water-insoluble powdery water-swellable substance into the raw material in the proportions shown in Table [1]. After kneading each composition in a mixer for 2 hours, it is first mixed on a calendar roll. , the above kneaded surface material is added to form a surface material layer, then the kneaded core material is added to form a core layer on the surface material layer, and finally the kneaded surface material is added again. A surface material layer was further formed on the core material layer to form a three-layer structure, and this was vulcanized and molded to obtain a gasket material. The physical properties of the gasket thus obtained are shown in Table [1]. Water-swellable substance used in the above examples: Fibrous water-swellable substance AN-based fiber (single fiber fineness: 3d, fiber length: 3mm) consisting of 90% acrylonitrile (AN) and 10% methyl acrylate (MA) , intrinsic viscosity in dimethylformamide (DMF) solution at 30°C;
1.3) Water-swellable fibers with a water swelling degree of 200 c.c./g were obtained by immersing 5 parts in 95 parts of a 30% caustic soda aqueous solution, boiling for 10 minutes with stirring, and then washing off the residual alkali with water. Ta. When the fiber was squeezed in a water-swollen state, it was found that it had an AN polymer core. Powdered water-swellable substance AN-based copolymer containing 90% acrylonitrile (AN) and 10% methyl acrylate (MA) (molecular weight: dimethylformamide (DMF) at 30°C)
Intrinsic viscosity measured in solution [η] = 1.5) 17 parts to 10
% caustic soda aqueous solution and at 90°C.
By stirring for 45 minutes, the sodium acrylate approx.
An aqueous solution of the polymer containing 70% and about 30% acrylamide was obtained. Next, after neutralizing the aqueous solution of this polymer with an aqueous sulfuric acid solution, 5.6 parts of a 30% formaldehyde aqueous solution was added to 100 parts of the polymer,
Stirred at 90°C for 15 minutes. After that, 60 at 200℃
The particles were dehydrated and dried by heating for 30 minutes to obtain water-swellable particles having a water swelling degree of 200 c.c./g and pulverized to 50 μm or less.

【table】

[Table] Seal test (1) Place the gasket between the flanges and apply a surface pressure of 20Kgf/
After tightening at ^cm2 , maximum 5 in 0.5Kgf/ ^cm2 increments
Apply water pressure up to Kgf/cm ² and check for leaks. The standing time at each water pressure was 10 minutes. Seal test (2) Place the gasket between the flanges and apply a surface pressure of 20Kgf/
After tightening to cm ² , apply water pressure of 2Kgf/cm ² , -
Repeat the cooling/heating cycle of 1 hour at 30℃ and 1 hour at 120℃ up to 100 times to check for leaks.

[Brief explanation of drawings]

The drawing is a sectional view of a gasket showing an embodiment of the present invention. 1... core material, 2... surface material.

Claims (1)

[Scope of Claims] 1. A gasket formed by vulcanization molding into a three-layer sheet of a core material composition and a surface material composition laminated on both sides thereof, wherein the core material composition is made of a fiber material of 50 to 90%.
% by weight, rubber material 10-50% by weight and water-insoluble water-swellable substances of acrylic polymers, polyvinyl alcohol polymers, starch polymers, nitrogen-containing cyclic polymers, and polyoxyethylene polymers. The surface material composition contains 1 to 23% by weight of at least one fibrous water-swellable substance, and the surface material composition contains 50 to 90% by weight of the fibrous water-swellable material.
10-50% by weight of a rubber material and 1-38% by weight of at least one powdered water-swellable substance of the water-insoluble water-swellable substance. 2 The length of the water-insoluble fibrous water-swellable substance is
The gasket according to claim 1, wherein the gasket has a diameter of 0.1 to 10 mm. 3. The gasket according to claim 1, wherein the thickness of the surface material composition on one side is 1/3 or less of the total thickness of the gasket and 10μ or more.